An electronic temperature sensor circuit can be arranged to measure the temperature on a remote (separate) silicon chip by providing one or more known currents to a p-n junction located on the remote chip. This circuit measures a diode voltage of this p-n junction and processes the diode voltage to determine the actual temperature at the remote location. Most p-n junctions employed for this purpose are parasitic vertical p-n-p silicon based transistors. Also, the temperature sensor circuit is usually arranged to control the emitter currents of the transistor.
The classic diode equation is often employed to determine the actual temperature at the remotely located p-n-p transistor based on a ratio of approximated collector currents. So long as the emitter current and collector current are substantially equivalent for this remotely located transistor, the determined temperature can be relatively accurate. However, if the beta (ratio of collector current over base current) of the p-n-p transistor varies with a varying emitter current, a determined temperature based on the diode equation can be less accurate. Recently, process variations and the ever shrinking physical size of process geometries for silicon devices are causing the beta to vary significantly with a varying emitter current.